1. Field of the Invention
The present invention relates to a display device, and more particularly, to a two-dimensional and three-dimensional image selectable display device which can display a two-dimensional image or a three-dimensional image by user's selection.
2. Discussion of Related Art
Autostereoscopic three-dimensional image display method is classified into a parallax method, a lenticular method, and an integral photography method. The parallax method enables the image to be divided and viewed through an aperture of a longitudinal lattice in front of each image corresponding to the left and right eyes. The lenticular method uses a lenticular plate arranged with a semi-cylindrical lens. The integral photography method uses a lens plate of the fly's eye shape.
A three-dimensional image display method employing special glasses has an advantage in that many observers can enjoy a three-dimensional image, but has a disadvantage in that it requires the observers to wear the special glasses, thus causing the inconvenience. The special glasses may be a pair of polarization glasses or liquid crystal shutter glasses.
The autostereoscopic three-dimensional image display method has a fixed observation region and thus only a limited number of viewers can enjoy the three-dimensional image. This method, however, may be preferred because it does not require separate glasses. As a result, extensive research is in progress in the area of autostereoscopic three-dimensional image display because in this area, the observer may directly view the screen.
The holographic display method is suggested as an example of displaying a perfect three-dimensional stereo image, which directly displays an image in a three-dimensional coordinate system in space usually through using laser, lens, mirror, etc. The holographic display method can provide three-dimensional stereo image having focus adjustment, vergence angle, binocular disparity, motion parallax, etc., which are factors causing the three-dimensional effect. The holographic display method is classified into a laser light reproduction hologram method and a white-colored light reproduction hologram. Hence, using the holographic display method, it is possible to have the same perception of reality as having the actual object before the viewer, but the holographic method is difficult to implement and the space occupied by the equipment is large.
Therefore, the tendency for employing parallax barrier is on the rise. The parallax barrier is a method of virtually implementing the three-dimensional image through an optical illusion using the stereo image.
The parallax barrier method places a longitudinal or transverse type (slit) in front of the image corresponding to the left/right eyes and causes the stereo image synthesized through the slit to be separated and viewed to perceive the three-dimensional effect.
The three-dimensional image display device by the parallax barrier method will be briefly described below.
FIG. 1 shows a three-dimensional image being formed by a conventional barrier method three-dimensional display device.
Referring to FIG. 1, a barrier panel 20 including slits, through which the light from an image panel 30 penetrates, and a barrier, which screens the light, are arranged in front of the image panel 30.
An observer 10 views images displayed or printed on the image panel 30 through the slits of the barrier panel 20. The left eye L and the right eye R of the observer 10 view different regions of the image panel 30 even when the image panel is viewed through the same slit. The parallax barrier method utilizes the above principle, which enables the observer to perceive the three-dimensional effect because the left and right eyes view different regions of the image through the same slit.
That is, the left eye L views the pixel Lp corresponding to the left eye on the image panel 30, and the right eye R views the pixel Rp corresponding to the right eye on the image panel 30 in FIG. 1.
However, using the conventional parallax barrier method three-dimensional display device it is very difficult to view a two-dimensional image as long as the barrier panel 20 is installed and provided in front of the image panel 30. Therefore, in the conventional parallax barrier method three-dimensional display device, the barrier panel should be eliminated to view a two-dimensional image.